Abstract
Operating a vehicle is a form of complex skilled behavior, which requires the driver to be alert. Sleepiness and fatigue behind the wheel are important causes of driver errors and traffic accidents and are associated with sleep deprivation, sleep disorders, circadian factors, use of recreational or medicinal drugs, monotonous conditions,
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and long driving times. Psychoactive substances play a important role in the context of drowsy driving. Drug treatment of underlying disorders may improve performance, but these drugs can also cause residual effects. Two main classes can be identified: the sedatives, most importantly hypnotic drugs, and psychostimulants. In order to advise drivers and health care providers about the benefits and risks of these substances, it is of importance to assess their respective effects on driving ability. A survey showed that sleep specialist know that there are risks for traffic participation, but there opinionas are not always congruent with the available literature. In addition, the effect of treatment of a number of sleep disorders on driving ability is still unknown. The currently available medicinal treatment options for insomnia belong to the class of benzodiazepine receptor agonists (BZRAs). In previous studies, it was shown that these drugs lead to residual effects on driving performance in the morning after intake. In addition, most BZRAs lead to postural balance impairments. Ramelteon is a novel prescription hypnotic that does not belong to the class of BZRAs. It is a melatonin agonist, which lacks affinity for most receptors associated with adverse effects and which did not lead to residual effects in previous studies. However, an on-the-road driving study was conducted that showed that ramelteon impairs driving performance, delayed memory recall, and psychomotor functioning. Unlike the BZRAs, ramelteon did not lead to balance disturbances at peak plasma levels. In terms of traffic safety, ramelteon cannot be regarded as an improvement compared to the current hypnotic drugs. The golden standard for driving studies is the on-the-road driving test on the highway in actual traffic. However, driving simulators have advantages in terms of costs, standardization and safety. A method was developed to examine the effect of psychoactive substances in the STISIM driving simulator and a calibration was performed. The results showed a dose-dependent impairment after the intake of alcohol. This confirms that the highway driving test scenario is sensitive to alcohol-induced impairments, and as such suitable for future pharmacological research. In addition, the differences compared to placebo that are obtained can serve as reference values for impairment seen with other drugs. This highway driving scenario was used to develop a sleepy driver paradigm in which participants drove for 2 hours, then had a 15-minute break in which a sleepiness countermeasure was administred, followed by driving for 2 more hours. The aim was to mimick highway driving, which is characterized by prolonged hours behind the wheel in monotonous conditions. Two commonly available countermeasures were tested: coffee (80 mg caffeine) and Red Bull® Energy Drink (250 ml). Both substances alleviated subjective sleepiness and improved driving performance in non-sleep deprived individuals.
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